One of them things you can't read in a book? I can't find it anyway.
What's the proper way to orient a 90-degree brass fitting to the proper angle to make a connection? I searched and researched this with no joy, so any pointers would be greatly appreciated!
When I screw in the 90-degree brass fitting on the left side of my M38 fuel pump (for the short rubber fuel input hose from the tank) the fitting won't snug down into the body of the pump at anywhere near a good angle to connect the hose. It's either loose, or so tight I don't even want to think about trying to wrap it around one more turn, especially on a $250 pump.
A lock nut seems to be out. Blue lock tight? Cherry pick fittings to find the right one? I'm being a wimp and just crank it around once more?
Thanks for some advice!
Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
Generally adding a thread sealant helps with the indexing. Most people tend to go way over torque with those brass pipe threaded nipples. If sealant and/or new fitting doesn't solve the issue the next step is to cut off the first couple of threads on the fitting and see if a slight change to travel distance helps.
Pipe threads are tapered so when it stops; it stops. Only real way is to buy another fitting and see it it will turn up like you want. They are randomly threaded so every one is different.
And as stated, do to over tighten them.
Thank you gentlemen. I've run through the few fittings I have with no joy. Cast aluminum fuel pump housing so I'm taking it easy. Hate to buy more fittings with little chance of success.
I was almost ready to start trimming threads off when I found some 1/8 NPT brass lock nuts at McMaster-Carr. Kind of pricey at $2.75 each delivered, but worth a try I thought.
McMaster-Carr # 50785K141
I test fitted one and think it might work!
Me thinks better to have the jeep police deduct 2 points rather than strip the hole or have a fuel leak on a loose one.....
Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
Pipe threads are tapered so when it stops; it stops.
Not quite true. Yes there is a point where a pipe thread will either not tighten anymore because you ran out of muscle or the female hole cracked. But if you approach the desired angle slowly and cautiously and when it aligns then leak check the fitting. If it leaks then you will need another turn or a hardening thread sealer. There are torque charts for pipe threads. Using a torque wrench is not the only method know to mankind. Counting rotations past finger tight is one way.
Here's a couple of pages everyone not familiar with the art of securing pipe threads should print and leave on the work bench.
CAUTION: Never back off an installed pipe fitting to achieve proper alignment. Loosening installed pipe fittings will corrupt the seal and contribute to leakage and failure.
I've been using PTFE sealant on the threads --- now have to wonder --- because I have backed off a tad on some of them to get the indexing (orientation) right on. The label on the PTFE says they can be re-positioned up to 12 hours later without compromising the seal. I know M38 fuel pressure is about 3 p.s.i. so I hope the nugget is intended more for high pressure stuff?
Thanks Wes!
Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
Most of us old farts are fully aware of these little nuggets. The same rule applies to fasteners that must be torqued but use a cotter pin. Never loosen to line up pin always tighten.
Had this problem on a couple fittings on my tractor. If there's any meat left on the fitting you can hit it with a pipe thread die and move the threads further up the fitting. On many brass fittings when they run the die on (to form the threads) they run it as far as it can go, which is where the die hits the 90 degree turn in the fitting........but on some I've seen they leave a little unthreaded.
You only want to add threads in the amount you need to turn the fitting to get it to fit. You go too far and you're screwed. Be careful with threadlocker.....medium blue is as strong as I'd go. Red is basically epoxy and you can't undo it without heat. And we all know how well heat and fuel get along.
Great stuff! The kind I can't read between the lines in a book. Give a man a fish, or teach him to fish. Much appreciated!
I must admit it never occurred to me to buy a 1/8 NPT die (don't know why, rookie I guess). For $10 I'm going to give it a shot.
wesk wrote:Most of us old farts are fully aware of these little nuggets.
I spend a lot of time searching and researching the interweb and this forum for nuggets that aren't in manuals. I'm learning that once I've decided I need to ask, a majority of the time things boil down to what exact question to ask, and then how to ask it (so it doesn't spin off into left field). A skill in itself. <after I get past mis-spelled words, which has taught me innovation with the search function>
I'm 62. Maybe one day I'll be an old fart too!
Thanks again gentlemen! Your patience is solid gold.
Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
I'm not sure that's gonna work..........but please let us know. By using the lock nut that means the pipe threads of the brass fitting aren't tight in the fuel pump.....ie, if the locknut wasn't there the fitting would thread further into the pump housing. So fuel will get past the threads of the housing and the fitting. Unless the locknut is sitting perfectly flat on the pump for a full 360 degrees....and the threads between the locknut and the fitting are perfect.......it's gonna leak.
I'm not sure if you're on the low or high pressure side of the pump. If it's the low side a bit of yellow Teflon tape on the threads and a thin gasket between the locknut and the pump might do the trick. Or maybe it'll be just fine as it is......ya never know. Looking forward to hearing how this turns out.
